<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        *{
            padding: 0;
            margin: 0;
        }
        .box{
            display: flex;
            margin: 20px;
            width: 300px;
            height: 300px;
            border: thistle solid 1px;
            flex-wrap: wrap;
            /* justify-content: space-between; */

        }
        .inner{
            width: 100px;
            height: 100px;
            background-color: turquoise;
        }
        .inner:first-child{
            margin-right: calc(100% / 3);
        }
    </style>
</head>
<body>
    <div class="box">
        <div class="inner">1</div>
        <div class="inner">2</div>
        <div class="inner">3</div>
        <div class="inner">4</div>
        <div class="inner">5</div>
        <div class="inner">6</div>
        <div class="inner">7</div>
        <div class="inner">8</div>
    </div>
</body>
</html>